What is this lump on my shoulder it is brown, hard and has been there for about 5 months. It got kind of smaller but has not gone away and it has never hurt the entire time it's been there. I'm a 19 year old female

Without . Without seeing the lesion in question it's very difficult to say. Some common things that could present as a painless, hard, brown lump on a shoulder could be: seborrheic keratoses actinic keratoses wart neurofibroma common mole these are possibilites. It will be up to your primary care provider or dermatologist to make a diagnosis. Good luck.